The present invention relates to an improvement in a keyboard construction and, more particularly to a keyboard construction adapted to unify an upper member of a housing for an electronic apparatus and a family of key actuators in the keyboard construction.
A conventional flat keyboard on an electronic apparatus such as a hand-held calculator includes a flexible sheet of plastic leather material constituting a plurality of movable key actuators, an upper member of a housing and a reinforcing frame for reinforcement of the flexible sheet and the upper member. The flexible sheet is sandwiched between the upper member and the reinforcing frame and secured tightly on the upper member. A sheet of nonconductive, elastic rubber and a circuit board are disposed beneath the flexible sheet. A plurality of conductive rubber bridging contacts are adhered to the nonconductive rubber sheet each corresponding in position to stationary contacts formed on the circuit board. The rubber sheet and the circuit board are secured within a lower member of the housing by a well known manner. The plastic leather sheet, however, is vulnerable to flaws and is difficult to restore from a depressed position to its initial one due to fatigue. Thus a more desirable material for the key actuator material is necessitated to overcome the deficiencies of the plastic leather sheet. Moreover, the use of plastic leather as the key actuator material is not compatible with indicia printing. As stated above, the reinforcing frame reinforces the actuator sheet and the upper member acts not to exert gravity of the nonconductive rubber sheet upon the actuator sheet. To make sure that a selected or depressed key in the key construction comes into effect for the introduction of inputs, the corresponding key actuator should be rather strongly actuated to pass through a central hole of the reinforcing frame. There is, however, a tendency for the actuator sheet to remain depressed due to fatigue even after the depression is released. Also, the appearance of the electronic apparatus is disfigured. In addition, a metallic sheet is needed within the keyboard construction for the purpose of shielding the keyboard construction against static electricity.